Applicants claims priority under 35 U.S.C. xc2xa7119 of German Application Nos. 100 27 315.7, 100 27 316.5 and 200 09 868.3, all filed Jun. 5, 2000.
1. Field of the Invention
The invention relates to a paring device for cylindrical objects, in particular for plastic tubes, comprising a plurality of rollers assembled to form a running trough; at least one paring knife; and at least one paring head having a guide roll; as well as a spindle drive connecting the running trough and the paring head. The spindle drive includes a spindle guide provided with a slot-shaped opening and a spindle rotating in the opening and having an actuation handle, whereby the paring head and the running trough, between which the cylindrical object can be fixed, can be driven against each other.
2. The Prior Art
The surfaces of tubes, cables or cylindrical rods frequently have to be worked before they are processed further. For example, it is necessary to remove an insulation layer from cables. Also, before welding plastic tubes, the surface of the tubes have to be pared. This process removes dirt accumulated from the manufacturing process, as well as material changes caused by aging, which may appear on the surface, for example due to damage caused by UV-radiation or weathering. Otherwise inadequate welding would result.
To remove a surface layer that is as thin as possible from the object to be worked in an exact manner, the cutting depth of the knife has to be exactly adjusted. This adjustment of the knife, which is required when the cutting depth is changed or when the knife is exchanged, requires skill and much experience on part of the machine operator. If the knife is aligned incorrectly, only inadequate quality of the treatment is frequently achieved. Either too much material is removed from the objects to be worked, which for tubes may reduce the remaining cross section to an inadmissible extent, or surface layers damaged by age or inclusions of dirt are not removed completely. If the knife is aligned in an inclined manner, it is possible that undesirable scores or grooves remain on the object to be pared, which may impair the welding process.
Products with rolled shoulders exhibit a certain ovality conditioned by the manufacturing process, which appears even in tubes with a large diameter due to longer storage periods. Such ovality of tubes is deemed undesirable during paring because with a fixed spacing between the running rollers and the knife on the paring head, such ovality causes the machining process to become irregular and unclean, so that it is not possible to obtain satisfactory treatment results. In extreme cases, areas of the tube may remain unworked, whereas other areas of the tube are pared to an impermissible depth.
For removing a surface layer from tubes or similar objects, a paring device of the type specified above is known, for example from DE 93 05 220 U, in which the paring knife is connected with the paring head in a fixed manner. In this paring device, the cutting depth of the paring knife has to be exactly adjusted in order to exactly pare from the object to be treated a surface layer that is as thin as possible. This exact adjustment is required whenever the cutting depth is changed, as well as with each exchange of the knife in order to avoid obtaining a treatment that is poor in quality due to incorrect alignment of the paring knife.
Furthermore, it is known in connection with paring knives to align the guide roll with a slanted setting in relation to the direction in which the running rollers of the running trough are running, in order to drive the paring device in the axial direction of the object to be pared, such as a tube or the like. The paring device can be guided in this way around the object with a helical movement, whereby the pitch associated with the slanted position of the guide roll has to be adapted to the diameter of the object, as well as to the width of the paring knife.
For special applications such as, for example for attaching tube clamps for drilling, or tube junctions to plastic tubes, it is necessary to pare only half of the circumference of the tube. However, with the conventional paring device described above, it is possible only to continuously pare the entire circumference of the object to be treated without discontinuing the treatment, and to axially displace the paring device on the object to be pared. Paring only half of the circumference of the tube, thus a saddle zone on the tube, is difficult to achieve with the known paring device. Furthermore, space is limited on construction sites, particularly in construction pits when drilling clamps have to be mounted or tube branches attached at a later time, to the extent that a conventional tube scraper cannot be employed in most cases.
Therefore, the problem of the invention is to provide a paring device that, in addition to treating the entire circumference of the object to be pared, is suited for treating saddle zones on a cylindrical object as well, without deteriorating in this way the handiness or the quality of the treatment process.
This problem is solved according to the invention in that at least one guide roller rotates freely about its own axis in a bearing block mounted on the paring head. The bearing block is freely pivoted about an eccentric axis perpendicular to the guide roller axis. As the paring device moves around the cylindrical object to be pared, the axis of the guide roller swivels to an angle relative to the axis of the object, so that the paring device moves helically around the cylindrical object. When the direction of movement of the paring device is reversed, the bearing block pivots as well, so that with an alternating movement of the paring device around half of the circumference of the cylindrical object, the paring device is always advanced in the same axial direction. It is thus possible with the paring device as defined by the invention to pare also the area of a cylindrical object required for drilling clamps or tube branches without having to work the complete circumference of the object. It is therefore possible to distinctly reduce the time required for working a cylindrical object without any change in the quality of the treatment when only the required surface areas are scraped off. Because the center of rotation of the bearing block is located outside of its center, the entire bearing block, as the paring device is moving, will automatically swivel into a position that effects an axial advance of the paring device on the object to be pared.
Two coaxial guide rollers are preferably supported in the bearing block. Guiding the paring device on the cylindrical object to be pared is enhanced in this way. Inaccuracies caused in the course of the treatment such as paring the same spot a number of times, or the formation of grooves are also avoided.
Furthermore, the bearing block may be elastically secured on the paring head. It is possible in that way for the guide rollers to apply contact pressure on the object to be pared.
As an alternative to the above, it is possible to support the guide rollers themselves in the bearing block in an elastic manner. A constant contact pressure of the guide rollers against the object to be pared can be achieved in this way as well, so that a high treatment quality is achieved through high guiding accuracy.
According to a preferred embodiment of the invention, the axes of the guide rollers can be aligned and fixed in at least one angular position in relation to the axis of the object to be pared. The pitch of the helical movement at which the paring device is driven around the object can thus be adjusted in a fixed manner. The operator is able in this way to assure that the cutting width of the paring knife is not exceeded by the pitch, so that a high treatment quality can be achieved. For differently sized diameters of the objects to be pared, the pitch can be adjusted via the inclined position of the axes of the guide rollers in such a way that optimal cutting width can be achieved.
It is preferred as a further development of the invention that a setscrew be provided on the bearing block for fixing the bearing block in relation to the paring head. By means of the setscrew it is possible to fix the alignment of the bearing block in relation to the paring head quickly and effectively. Any change in the alignment of the bearing block in relation to the paring head can be quickly carried out as well, for example when an object with another diameter has to be worked, or when the width of the knife is varied.
According to the invention, two protrusions may be formed on the paring head, between which the bearing block can be swiveled. In this way, it is possible to avoid swiveling of the bearing block to any excessive degree, which would make it impossible to exactly guide the paring device on the object to be pared. The range within which the bearing block can be swiveled is preferably adjustable, so that the paring device can be adapted to different pitches.
According to another embodiment of the invention, the paring knife comprises a blade that is received in a sliding shoe and forms one single piece with the latter, whereby the sliding shoe is secured on the paring head in a detachable manner. In this way, the sliding shoe rests against the object to be pared and therefore permits good guidance of the blade of the paring knife on the object to be pared. It is possible in this manner to achieve a particularly uniform cutting depth and thus a constant cutting quality. Furthermore, the single-piece embodiment of the sliding shoe with the blade offers the advantage that complicated adjustments of the knife can be dispensed with. The blade is already aligned at the correct angle in relation to the sliding shoe and joined with the latter when it is manufactured, so that the sliding shoe supporting the blade then only needs to be secured on the paring head.
The sliding shoe preferably comprises two sliding surfaces that are spaced from one another by a recess. The sliding surfaces rest against the object to be worked and guide the blade of the paring knife. Any canting of the blade of the paring knife can be avoided by providing the sliding shoe not only with one but with these two sliding surfaces that are spaced from each other. When the two sliding surfaces rest against the object to be worked at the same time, high paring accuracy is achieved.
According to another advanced development of the invention, the blade of the paring knife is arranged in the recess of the sliding shoe, whereby the blade projects beyond the sliding surface of the sliding shoe by sections. The blade of the paring knife is thus guided between the two sliding surfaces of the sliding shoe. Any canting of the blade on the object to be pared can be avoided in this way.
According to another preferred embodiment of the invention, the blade is connected with the sliding shoe via a screw connection on the paring head. The blade with the sliding shoe can be quickly exchanged in this way by simple means. Preferably, only one single screw is required for securing the blade with the sliding shoe on the paring head.
As an alternative to the above, the blade with the sliding shoe is secured on the paring head via a locking connection. The installation and removal of the blade with the sliding shoe on the paring head can be facilitated in this manner even more because the blade can be secured on or detached from the paring head via the locking connection without using any tools. Controlling the paring device as defined by the invention is made distinctly easier in this manner.
The blade preferably is a reversible blade ground on two sides. The paring knife thus has its own spare blade. In this way, the number of spare parts to be kept available for the paring device can be reduced, and the manufacturing and operating costs remain low as well. Furthermore, it is also possible to obtain with the reversible blade two different cutting depths with only one single blade if the two ground sides of the reversible blade protrude beyond the sliding surfaces of the sliding shoe to different degrees.
According to another embodiment of the invention, the sliding shoe is elastically secured and/or secured on the paring head in a tilting manner. Variations in the roundness such as ovalities or the like of the object to be worked can be compensated in this manner by the paring device as defined by the invention, as can be inaccuracies in the axial direction, without having to readjust the spacing between the running trough and the paring knife in the course of the paring operation. Handling of the paring device can be simplified in this manner and the treatment result can be distinctly enhanced at the same time. Furthermore, by initially tensioning the knife, a uniform contact pressure is achieved that can assure a constant treatment quality even when the paring device is operated over a longer period of time. Furthermore, the tilting capability of the sliding shoe prevents the blade from canting or assuming a slanted position, so that scores and the like can be avoided.
According to the invention, the knife holder can be swiveled around a bolt and be supported in the paring head with two springs acting on it. The construction of the sliding shoe with the blade can be kept simple in this manner because the elastic support of the sliding shoe is accommodated in the paring head, where adequate installation space is available for this purpose. Any replacement of the sliding shoe can be made easier as well because the entire elastic support does not need to be jointly replaced, but rather it is necessary only to release the fastening of the sliding shoe on the elastically supported knife holder. Handling of the paring device as defined by the invention is clearly made easier in this way.
According to yet another embodiment of the invention, the paring head and/or the running trough comprise a threaded section, via which the paring head and/or the running trough can be detachably engaged with the spindle via a snap lock.
This makes it possible to detach the threaded section from the spindle for the purpose of roughly adjusting the spacing between the running trough and the paring head, and to adapt such spacing to the diameter of the object to be treated without actuating the spindle. The spacing between the running trough and the paring head can then be finely adjusted by actuating the spindle as the spindle is being engaged by the threaded section of the paring head or the running trough.
Furthermore, an elastic element may be arranged in the spindle drive between the spindle and the spindle guide on at least one end. In this way, the spindle is maintained in the spindle guide under initial tension. Such initial tension is transmitted from the spindle to the paring head or the running trough via the treaded section. Deviations in the roundness such as ovalities or the like of the object to be worked can be compensated in this manner by the paring device without having to readjust the spacing between the running cup and the paring head in the course of the treatment operation. The handling of the paring device is made simpler in this manner and the treatment result can be distinctly increased at the same time.
As a further embodiment, an indicator element that is connected with the spindle and can be driven into the spindle guide at least by sections may be provided on the end of the spindle facing away from the actuation handle. If, after fixing an object to be treated, the spindle is displaced in the spindle guide between the running trough and the paring head against the force of the one or more elastic elements, the indicator element connected with the spindle is displaced as well, the indicator element projecting from the spindle guide when the spindle is in the unstressed state. The spring constant of the elastic axial support of the spindle can be selected in this connection so that the indicator element is located in a defined position at a defined force of initial tension and thus is, for example, aligned flush with the spindle guide. The force of the initial tension of the spindle can be read in this way via the position of the indicator element. With the help of the indicator element, the user can easily adjust an optimal initial tension of the spindle and thus achieve a good treatment quality.